Variable speed mechanism



Sept. 29, 1942.

R. J. IFIELD VARIABLE SPEED MECHANISM 4 Sheets-Sheet 1 Filed July 24, 1941 P 1943?-v R. J. IFIELD VARIABLE SPEED MECHANISM Filed July 24, 1941 4 Sheets-Sheet 2 Sept. 29, 1942- RpJ. IFIELD I VARIABLE SPEED MECHANISM Filed July 24, 1941 4 Sheets-Sheet 5 IL M a x Sept. 29, 1942. R. .1. IFIELD 2,296,929

VARIABLE SPEED MECHANISM Filed July 24, 1941 4 Sheets-Sheet 4 Patented Sept. 29, 1942 UNITED STATES VARIABLE SPEED MECHANISM Richard Joseph Ifleld, Elmdon, Heath, Solihnll, England, assignor to Joseph -Lucas Limited,

Birmingham, England ADl licationJuly 24, 1941, Serial No. 403,926 In Great Britain August 13. 1940 7 Claims. (Cl. 74-293) This invention has for its object to provide improved means for effecting a variable-speed connection between driving and driven members of a mechanically propelled vehicle or any other mechanism. v

The invention comprises the combination of an epicyclie gearing, a Pair of complementary rotary pumps. each having a plurality of reciprocatory plungers, and means fonvarying the strokes of the plungers, one of the pumps being associated with one part of the epicyclic gearing and the other pump with another part of the gearing.

In the accompanying sheets of explanatory drawings: l

. Figure 1 is a longitudinal section illustrating one form of variable speed mechanism constructed in accordance with the invention.

Figure 2 is a cross section on the line 2-1 (Figure 1) Figure 3 is a cross section on the line 3-3 (Figure 1).

Figure 3a is a section on the line 3a-3a (Fig-,- ure 3).

Figure 4 is'a cross section on the line ll (Figure 1).

Figure 5 is a cross section on the line 55 (Figure l) Figure 6 is a diagram illustrating'means by which the pumps are maintained in a fully charged condition.

Figures 7-11 are respectively diagrammatic representations illustrating different alternative embodiments'of the invention shown in Figures 1-5.

Referring to Figure 1, this illustrates a mechanism suitable for use in the power transmission system of a mechanically propelled .vehicle, but essentially the same mechanism can be employed for any other purpose in which it is required to eifect a variable-ratio connection be tween'driving' and. driven members of a power transmitting mechanism. As shown in Figure 1, the driving member is a wheel a, which may be the flywheel of an internal combustion/engine, andthe driven member is a shaft b, the two members being arranged coaxially. with each other, and the driven member being mounted in and adapted to extend from one end of a casing, 0 which at the other end encloses the drivingmemberh Also mounted within the casing c are two similar complementary pumps (1, e, which are situated in coaxial relationship with each other and with the driving and driven to pass through the pumps. The pump d comprises a rotary body part in the form of 8. cylinder block I provided with a plurality of longitudinal bores 9 containing reciprocatory plungers h, and associated with the outer ends of the plungers (which project from one end of the block) is an annular swash plate i having a pair of diametrically opposite trunnions as i whereby it is pivotally mounted in the casing 0 around the driven shaft b. The inclination of the swash plate 1' is adjustable by any convenient means. The face of the block 1 at the end remote from .the swash plate i bears against one side of a ported non-rotatable abutment is mounted in the casing c, and this end of the block is supported by a ball or roller bearing'm, the other end being supported by a ball or roller bearing n. At the opposite side of the abutment k is situated the other and similar pump e. This comprises a rotary body part in the form of a cylinder block 0 provided with longitudinal bores p containing reciprocatory plungers q, and associated with the outer ends oi." these plungers (which project from the end of the block remote from the abutment) is an annular swash plate 1' having a pair of diametrically opposite trunnions s whereby it is pivotally mounted in the casing 0 around the driven shaft b, the inclination of this swash plate being adjustable by any convenient means. The cylinder block 0 is supported by ball or roller bearings t, u, and the face of this block at the end remote from the swash plate r bears against the abutment k.

The abutment k is provided with a pair of 35 kidney-shaped ports 12 (Figure 2) the ends of which are separated by portions equal or substantially equal in diameter to the diameter of the plunger bores p in the cylinder blocks o. In this example each cylinder block is provided with an odd number of bores as shown in Figure 2.

When in action the pump plungers h, q serve to effect displacement of liquid between the bores g, p in the two cylinder blocks 1, 0. That is to say, while liquid is being displaced from f to 0 through one of the ports 2: liquid is being /displaced from o to I through the other port,

or vice versa.

Preferably, and as shown, the bores y, p 'are inclined to the axis of the pumps d, e, the adjacent ends of the bores being nearer-to this axis than the other ends. Also the plungers h, q are of hollow form, their innenends being open and their outer ends closed.

members a, b, the driven member being arranged The cylinder block 0 is secured to one end of situated adjacent to and of larger diameter than the sun pinion a: as shown. In association with the sun pinions :r, z, is arranged a rotary planet pinion carrier 2 secured to the driven shaft b. On this carrier are mounted two groups of planet pinions. One of these groups is composed of a plurality of twin pinions 3, 4, or different diameters. The smaller pinions 3 engage the larger sun pinion z, and the larger pinions 4 engage an internally toothed annulus 5 on the driving member a. The planet pinions 6 of the other group engage the smaller sun pinion a: and the larger planet pinions 4 of the first mentioned group.

Power is transmitted from the driving member a to the driven member I) through the sun and planet or epicyclic mechanism above described with a gradually variable ratio' which is determined by the pumps d, e. Assuming the swash plates 2, r, to be in the position shown in Figure 1, 1- being at right angles to the axis of the mechanism and i at its maximum inclination, it will be apparent no displacement of the plungers n can occur asliquid cannot in this condition be displaced from the cylinder block, 1 to the cylinder block 0, and consequently the block I will be held against rotation. The block 0 is however free to be rotated. by the epicyclic mechanism as rotation of this block (with the swash plate 1' in the position shown) involves no displacement of liquid between the two blocks 0, I. With the sun pinion .2 held stationary by the cylinder block I, the driven shaft b will be driven at a lower rate than the driving member a, and meanwhile the' cylinder block 0 will be rotated idly by the sun pinion 0:.

Assuming the relative positions of the swash plates 1', r, to be reversed, the plate 1' being arranged at right angles to the axis of the mechanism and the plate 1' moved (by a counter-clockwise rotation) to its position of maximum obliquity, the sun pinion a: will be held against rotation, and the shaft b will be driven at a higher rate thanthe driving member a, the cylinder block being meanwhile rotated idly by the sun pinion z. By varying the relative inclinations of the two swash plates 2', r, so that liquid displacement can occur between the pumps d,'e, under the action of the plungers h, q, thereby enabling both cylinder blocks 1, o, to rotate, any desired relative rotation of the two sun pinions :c, 2 can be produced (between the limits attainable with the swash plates in the two positions above described) with corresponding variations of the speed ratio between a and b. When the swash plates i, r, are situated at equal and opposite inclinations, the elements of the epicyclic mechanism rotate en bloc, and the members a, b, then rotate at equal speeds.

By the combination of an epicyclic mechanism, and complementary pumps operating as above described, the speed ratio of the driving and driven shafts is gradually variable by any desired amount within the limits for which the mechanism is designed.

when the relative inclinations of the two swash plates, 2', r, are such that liquid displacement occurs between the pumps d, e, liquid passes from one of the pumps to the other through one of the ports 22 at a high pressure determined by the load on the driven shaft b, and returns through the other or these ports at a relativelylow pressure. Moreover, the relative inclinations of the swash plates i, r, determine which of the two pumps d, e, causes the displacement of liquid under high pressure, and which of the two ports 12 is traversed by the high pressure liquid.

Under working conditions some slight leakage of liquid past the plungers h, q and the abutment k is unavoidable, and this is compensated by any convenient pump. The latter may consist as shown of an eccentric rotor l0 secured to the sleeve 3 and contained in a chamber ll within the casing c, and co-operating with a radially situated slidable vane 12 held in contact with the periphery of the rotor by a spring [3. In communication with the rotor chamber II at one side of the vane l2 there is formed in the casing 0 a liquid inlet passage I4 which serves to connect the rotor chamber to a sump l8 formed by the. lower part of the casing. At the other side of the vane I! the rotor chamber ll comsage l5 liquid for replenishing the pumps d, e,

can be supplied alternately to the two ports 1) in the abutment is under the control of a reciprocatory piston valve. 43 (see Figure 6). For enabling the valve 43 to be actuated automatically in response to the difference in the pressure at which liquid is displaced from either of the pumps d, e, to the other and the pressure at which this liquid is returned, the valve is slidable in a cylinder 44 which at one end is connected by a pipe 45 to one of the ports v, and at the other end is connected by a pipe 46 to the other of these ports. Also the valve 41 is provided as shown with a reduced intermediate portion and the annular space in the cylinder 44 around this reduced portion communicates with the delivery passage [5 through another pipe 41. Moreover the pipes '45, 46 are each provided with a branch 48 which is adapted to communicate with the cylinder 44 under the control of the adjacent end of the valve 43, the latter when in either of its extreme positions serving to establish communication between one of the branches and the pipe 41, and to close the other branch. When the mechanism is in operation the pipes 45, 46 and 41, the branches 48, and the parts of the cylinder 44 not occupied by the valve 43 are full of liquid. Moreover the valve 43 is movable between its extreme positions in response to the pressure difference above mentioned for interrupting communication between the delivery passage l5 and either of the abutment ports 12, and for establishing communication between the delivery passage and the other abutment port, the arrangement being such that while high pressure liquid is traversing either of the said ports this port is isolated from the delivery passage and replenshing liquid can flow to the other port only. Any convenient pressure relief valve as 49 may be provided for the liquid in the delivery passage 15.

To maintain a fluid-tight contact between the adjacent end faces of the cylinder blocks f, o, and abutment k, the latter is non-rotatably but slidably mounted in the casing 0 between the adjacent bearings m, t, of the blocks, and liquid pressure is exerted endwise on the block 1. For

enabling such pressure to be exerted there is provided in the casing c an annular chamber I containing a slidable piston-like packing 8 annular chamber 1 being full of liquid, and the arrangement being such that while high pressure liquid is traversing either of the abutment ports ,1), this port is in communication with the said annular chamber and the other port is isolated from the said chamber.

As previously indicated any convenient means may be employed for adjusting the inclination of the swash plate r, but I prefer to employ for this purpose the hydraulic means shown in Figure 3 and 3a. Such means comprise a hollow member I] which is journalled in a hearing I! on the casing c, and which at its inner end accommodates one of the trunnions s on the swash plate 1, this trunnion having a splined connection with the hollow member. The outer end of the hollow member I1 is formed at diametrically opposite positions with a pair of longitudinally arranged segmental projections H which are accommodated in segmental recesses 2| formed longitudinally in an enlargement 2| of the outer end of the bearing It, the arcuate peripheral surfaces of the projections fitting closely against the corresponding surfaces of the recesses, and the latter being sufllciently wider than the projections to permit angular movements of the hollow member ll between limits determined by contact of the sides of the projections with the sides of the recesses. Near its outer end the hollow member I1 is formed with two pairs of diametrically opposite ports projections l9 are full of liquid, and liquid under pressure is supplied to the pipe connection 29 from any convenient pump, which may be the replenishing pump (l0, H) above described. In the initial position of the control member 24 the lands 21 close the adjacent ends of the ports 22 in thehollow member H as shown in Figure 3a, and the liquid thus trapped in the segmental recesses 20 serves as a hydraulic lock for preventing angular movement of the swash plate 1'. The control member 24 is movable angu- 22 situated in planes at right angles to each other. One pair of the ports 22 communicate respectively with the recesses 20 at one side of the projections l9, and the other pair of the ports communicate respectively with the recesses at the other side of the projections, the arrangement being such that liquid admitted under pressure to the recesses through either pair of the ports and released through the other pair causes angular movement of the hollow member II for varying the inclination of the swash plate 1'. For controlling the flow of liquid to and from the recesses 20, a rotatable control member 24 is mounted in a cover 25 closing the outer end of the bearing enlargement 2|. The control member 24 extends into and fits closely the adjacent portion of vthe hollow member I1, and is formed in the vicinity of the portsg22 with two pairs of peripheral recesses 26. 26 disposed at 90 apart, these recesses being separated by lands 2'l slightly wider than the diameter of the ports. One oppositely situated pair (26) of the recesses communicate throughpassages 28 in the control member 24 with'a liquid inlet pipe connection 29 on the cover 25, and the other pair (26 of When the mechanism is in use the parts of larly to and from its initial position by any convenient means which in the form illustrated comprises a toothed rack 32 slidably supported by the cover 25 and engaging a pinion 33 on the side of the projections is released. The eflect of this is to cause the hollowmember II. together with the swash plate 1 to move in the same direction and to the same extent as the control member 24, whereupon the lands 2'! again close the adjacent ends of the ports 22 for causing the hollow member and swash plate to be locked in the new position by the liquid trapped in the recesses 20.

Means similar to those above described for adjusting the inclination of the swash plate 1' are also employed for adjusting the inclination of the other swash plate 1'.

Preferably and as shown each of the swash plates 5, r is composed of a pair of coaxially arable relatively to the outer part which is pivoted to the casing c as above described.

The form of the epicyclic gear and the manner in which it is connected to the pumps may be varied in a variety of ways, some of which will now be described with the aid of the 'diagrams shown in Figures '7 to 11 in which the same or analogous parts are indicated by the same reference characters as those employed in Figures 1 t0 6 with the addition-of distinguishing 111-.

dices.

The example shown in Figure 7 is similar to that shown in Figure l with the exception that the planet pinions 4 are in direct engagement with the smaller sun pinion 9: instead of being connected thereto through the intermediary of additional planet pinions. When the sun pinion 2 is locked the driven shaft is rotated at a lower speed than the driving shaft. Also when the sun pinion m is locked the driven shaft is rotated at a lower speed than the driving shaft, but faster than when the sun pinion 2 is locked. Between these limits the speed ratio is gradually variable plates.

The example shown in Figure 8 is suitable for use when it is desirable to mount the cylinder blocks f and 0 on an axis spaced from and parallel with that of the driving and driven members a, b. In this example the adjacent ends of the latter members are respectively provided with a planet carrier 2 and a sun pinion x, and on theplanet carrier are mounted a plurality of twin the segmental recesses 20 not occupied by the 1 shown in any of Figures 9 to 11;

secured to the driving member a cylinder block I. The larger pinions 4 engage the sun pinions 1: and an internally toothed annulus isecured toa gear wheel 4|. The gear wheel II is freely'mounted on the driving member 41 and is in engagement with another gear wheel 42, (of the same diameter as the toothed wheel 40) secured to andcoaxial with the cylinder block In all of the 'examples above. described 'both of the coaxially arranged .pumps are capable of rotation relatively to the driven member. But this is not an essential condition as one of these pumps may be secured to the driven member as In the example shown in Figure 9 the cylinder block 0 is secured on the driven shaft 1) which atthe end adjacent to the driving member a has secured to it an internally toothed annulus 31 of the same diameter asthe internally toothed annulus on the driving-member. The other cylinder block 1 is secured to one end of a hollow shaft 11 which is rotatable on the driven shaft b and which at its other end is formed or provided with a sun pinion z. Ar-

ranged coaxially with and adjacent to the sun pinion 2 is another sun pinion :c of the same diameter, the latter sun pinion being fixed. Arranged between and in engagement with the toothed annuli 5 31 and the sun pinions r 2 are twin pinions 3 4 mounted on a rotary car-' rier 2 When the swash plate 1' is at right angles to the axis, and the swash plate 1'? is inclined, the pump body'o and driven shaft 1: cannot rotate. The rotation of the driving member a thus results in idle rotation of the planet pinions, the sun pinion a and pump 1 .When the swash plate 1 is at right angles, and the swash plate i is inclined, the sun pinion a is locked and the driven shaft (with pump body 0 is rotated at the same speed as the driving shaft. Varia-' tion of speed ratio within the limits provided by this arrangement of gearing and pumps is effected by appropriate adjustment of the swash plates. I

In the example shown in Figure the cylinder block 0 is secured on the driven shaft 11* which at the end adjacent to the driving member a has secured to it a planet carrier 2 The other cylinder block I is secured to one end of a hollow shaft 1/ which is rotatable on the driven shaft b and which atits other end is formed or provided with a sun pinion x In engagement with the sun pinion a) are planet pinions 3- which are mounted on the carrier 2 and which also engage an internally toothed annulus 5 on the driving member a. The mode of operation of this arrangement is similar to that of Figure 9, in that the required variations of speed ratio within the limits of the mechanism are obtained a by appropriate adjustment of the swash plates.

The example shown in Figure '11 is similar to that shown in Figure 10 with the exception that the positions of the internally toothed annulus 5 and planet carrier 2 are interchanged, that is to say the toothed annulus is secured to the driven member b and the planet carrier is Here again the mode of operation for effecting the required variations of speed ratio is similar to that of Figure 9 or 10.

The inventionis not limited to the examples above described and from these examples it will be apparent that the invention is capable of being carried out in many different ways. But in all cases there is employed an epicyclic gearing, and the control of the speed ratio between the driving and driven members is eflected by a pair of pumps of the kind specified connected to two appropriate parts of the epicyclic gearing. Further the terms driving and driven" used in the above descriptions may be interchanged, the parts described as driving members being thus driven members, and the parts described as drivenmembers being driving members, and I wish it to be understood that these terms are used in this sense.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

'- 1. A variable-speed mechanism having in combination an epicyclic gearing, a pair of complementary pumps each comprising a rotary body part provided with a plurality of bores, and reciprocatory plungers in the bores, a ported nonrotatable abutment 'situatedjbetween and in contact with adjacent end faces of the pump body parts, the said body parts being rotatable relatively to and arranged coaxially with each other,

and angularly adjustable swashplates co-operating with the outer ends of the plungers for varying the strokes of the latter, one of the pumps being associated with one part of the epicyclic gearing and the other pump with another part of the gearing.

2. A variable speed mechanism as claimed in claim 1, in which the abutment is provided with a pair of kidney-shaped'ports which at their ends are separated from each other by distances of the order of the diameter of the plunger bores in the pump body parts.

3. A variable speed mechanism as claimed in claim 1 and having in combination means for supplying replenishing liquid to the pumps, and

a valve responsive to the difference in the pressures developed by the pumps for automatically connecting the said means to the pump region of lower pressure, the said difference being determined by the positions of the swash plates.

"4. A variable speed mechanism as claimed in claim 1 and having in combination means for supplying replenishing liquid to the pumps, and a valve responsive to the difference in the pressures developed by the pumps for automatically connecting the said means to the pump region of lower pressure, the said difference being determined by the positions of the swash plates, and the said means'consisting of a rotary pump embodied in and operatively associated with a rotatable part of the mechanism.

5. A variable speed mechanism as claimed in claim 1 and having in combination means for supplying replenishing liquid to the pumps, a valve responsive to the difierence in the pressures developed by the pumps for automatically connecting the said means to the pump region of lower pressure, the said difference being determined by the position of the swash plates, and piston-like means which is associated with and through which hydraulic pressure can be exerted endwise on one of the pump body parts, the said piston-like means being controlled by the valve associated with the liquid replenishing means.

and driven members and being connected to other parts of the gearing.

'1. A variable speed mechanism as claimed in claim 1 and having a driving member connected to one. part of the epicyclic gearing, and a driven member connected to another part of the said gearing, one o! the pump body parts being secured on one of the driving and driven members, and the other or the pump body parts being rotatable relatively to both thedriving and driven members and being connected to a third part of the gearing. Y

' RICHARD JOSEPH Irma). 

